Skin Displacement Research Articles

Measurement System for Finger Skin Displacement on a Textured Surface Using Index Matching

Understanding the relationship between the displacement of the skin when tracing a textured object and the resulting subjective sensations is essential in designing tactile displays. Previous studies observed skin displacement using flat glass plates or uneven surfaces that do not optically interfere with finger surface observations. In contrast, no direct method for observing skin surface displacement on a texture exists. We propose a system that enables observation of the interaction between a textured surface and the skin of the finger using an index-matching technique. In the proposed system, a texture plate is immersed in oil having the same refractive index as the plate, and measurements are made when the interface is nearly optically transparent. Further, printed markers are attached to the skin of the finger, and their movements analyzed using an image-processing algorithm. The system enables spatial measurement of the skin shear and the vibration of the contact area. Evaluation experiments conducted on a 1D textured surface having a pitch of 0.6 mm verify the feasibility of the proposed system. Optical misalignment simulation results indicate that the system is slightly less accurate than type-I mechanoreceptors but can measure skin deformation on a texture and also observe it spatially and temporally.

Facially expressive humanoid robotic face

Realistic humanoid robots have emerged in the last two decades but the emotional intelligence of these machines has been limited. To teach humanoids how to emotionally communicate with humans, researchers have been increasingly relying on machine learning algorithms. While the software used to implement machine learning algorithms is largely open source, facially expressive humanoid robots are expensive and inaccessible to most people, thus limiting the number of researchers in this field. This paper aims to aid potential artificial intelligence researchers by providing a relatively inexpensive, open-source robot that can serve as a platform for research into emotional communication between humans and machines. Eva, the robot described in this paper, is an adult-sized humanoid head that can emulate human facial expressions, head movements, and speech through the use of 25 muscles, including 12 facial muscles that can produce a maximum skin displacement of 15 mm.

Effect of scanning speed on texture-elicited vibrations.

To sense the texture of a surface, we run our fingers across it, which leads to the elicitation of skin vibrations that depend both on the surface and on exploratory parameters, particularly scanning speed. The transduction and processing of these vibrations mediate the ability to discern fine surface features. The objective of the present study is to characterize the effect of changes in scanning speed on texture-elicited vibrations to better understand how the exploratory movements shape the neuronal representation of texture. To this end, we scanned a variety of textures across the fingertip of human participants at a variety of speeds (10–160 mm s−1) while measuring the resulting vibrations using a laser Doppler vibrometer. First, we found that the intensity of the vibrations—as indexed by root-mean-square velocity—increases with speed but that the skin displacement remains constant. Second, we found that the frequency composition of the vibrations shifts systematically to higher frequencies with increases in scanning speed. Finally, we show that the speed-dependent shift in frequency composition accounts for the speed-dependent change in intensity.

The Influence of the Insertion Angle on Middle and Lower Face Tissue-Mechanics When Treating the Nasolabial Folds with Facial Suspension Threads-An Experimental Split-Face Cadaveric Study.

A novel treatment approach to address the nasolabial fold is the insertion facial suspension threads. However, there is a paucity of data available to guide insertion techniques and material selection. Three female and two male cephalic specimens of Caucasian ethnicity (73.6 ± 6.5 years; 21.41 ± 2.2 kg/m2) were included into this experimental split-face study. One facial side was treated with polycaprolactone (PCL) thread: 180 mm, bidirectional, 18G 100 mm cannula, 20 degrees trajectory, preauricular approach whereas the contralateral side was treated with polydioxanone (PDO) thread: 100 mm, bidirectional, 19G, 60 mm cannula, 50 degrees trajectory, infraorbital approach. Three-dimensional imaging outcome measures included vertical and horizontal skin displacement and volume changes at the nasolabial sulcus, at the labiomandibular sulcus, and along the jawline. Comparing PCL 180 mm 20 degrees to PDO 100 mm 50 degrees: vertical lifting effect 1.42 ± 2.63 mm versus 1.24 ± 1.88 mm (p = 0.906); horizontal lifting effect 3.42 ± 1.44 mm versus -2.02 ± 1.84 mm (p = 0.001); nasolabial volume change -0.80 ± 0.65 mL versus -0.52 ± 0.17 mL (p = 0.367); labiomandibular volume change -0.45 ± 0.42 mL versus -0.16 ± 0.16 mL (p = 0.191); jawline volume change 0.02 ± 0.43 mL versus -0.01 ± 0.21 mL (p = 0.892). The study provides objective evidence for the short-term effectiveness of facial suspension threads in treating the nasolabial folds. The results point toward a better aesthetic outcome when utilizing long facial suspension threads that can effect full-face changes as compared with short facial suspension threads.

The Bidirectional Movement of the Frontalis Muscle: Introducing the Line of Convergence and Its Potential Clinical Relevance.

Cosmetic treatment of the forehead using neuromodulators is challenging. To avoid adverse events, the underlying anatomy has to be understood and thoughtfully targeted. Clinical observations indicate that eyebrow ptosis can be avoided if neuromodulators are injected in the upper forehead, despite the frontalis muscle being the primary elevator. Twenty-seven healthy volunteers (11 men and 16 women) with a mean age of 37.5 ± 13.7 years (range, 22 to 73 years) and of diverse ethnicity (14 Caucasians, four African Americans, three Asians, and six of Middle Eastern descent) were enrolled. Skin displacement vector analyses were conducted on maximal frontalis muscle contraction to calculate magnitude and direction of forehead skin movement. In 100 percent of investigated volunteers, a bidirectional movement of the forehead skin was observed: the skin of the lower forehead moved cranially, whereas the skin of the upper forehead moved caudally. Both movements converged at a horizontal forehead line termed the line of convergence, or C-line. The position of the C-line relative to the total height of the forehead was 60.9 ± 10.2 percent in men and 60.6 ± 9.6 percent in women (p = 0.941). Independent of sex, the C-line was located at the second horizontal forehead line when counting from superior to inferior (men, n = 2; women, n = 2). No difference across ethnicities was detected. The identification of the C-line may potentially guide practitioners toward more predictable outcomes for forehead neuromodulator injections. Injections above the C-line could mitigate the risk of neuromodulator-induced brow ptosis.

Behaviorally measured tactile sensitivity in the common bottlenose dolphin, Tursiops truncatus

AbstractLittle research has been conducted on the somatosensory system of toothed whales and it remains uncertain how tactile sensitivity varies about their bodies. In this study, tactile sensitivity to high‐frequency (250‐Hz) displacement of the skin was quantified in three trained adult common bottlenose dolphins (Tursiops truncatus) using a vibratory device (tactor). The magnitude of skin displacement was controlled by varying the voltage to the tactor held against the skin surface with a constant force. Tactile thresholds were determined using an adaptive method of limits in which dolphins reported perception of the tactile stimulus by producing a whistle. Displacement thresholds ranged from 2.4 to 40 μm, with the greatest sensitivity found along the rostrum, melon, and blowhole. Sensitivity decreased caudally along the body, with the dorsal fin and tip of the fluke being the least sensitive locations tested. The results support hypotheses that the follicles on the dolphin rostrum are particularly important for perception. The reduction in tactile sensitivity at the appendages is consistent with their primary role in stabilization and locomotion compared to exploration or environmental sensing.

Physics of Within-Tissue Wave Propagation Generated by Pulse Propagation in the Carotid Artery

(1) Background: We aimed to assess the validity of laser Doppler vibrometry (LDV) as an emerging method to measure the local pulse wave velocity (PWV) from skin displacement generated by the pressure pulse inside an underlying artery. (2) Methods: A finite element model representing a simplified common carotid artery embedded within a soft tissue mimicking material was used to reproduce how tissue motions due to a wave propagation along the artery radiates to the skin surface. A parametric study was set up, varying: (i) the pressure conditions inside the artery (shock and traveling pressure impulse), (ii) the arterial depth and (iii) the geometry in a patient-specific artery model. (3) Results: under all conditions, the arterial pulse induced primary and secondary waves at the skin surface; of which the propagation speed deviated from the imposed PWV (deviations between −5.0% to 47.0% for the primary wave front). (4) Conclusions: the propagation of a short pressure impulse induced complex skin displacement patterns revealing a complicated link between PWV and measured propagation speeds at the skin surface. Wave propagation at the skin level may convey information about arterial PWV, however, advanced signal analysis techniques will be necessary to extract local PWV values.

Relationship between forehead motion and the shape of forehead lines-A 3D skin displacement vector analysis.

Neuromodulator injections of the forehead are often performed using standardized protocols. This study was designed to identify the individual skin motion pattern of the forehead and to relate this pattern to the underlying frontalis muscle morphology to offer guidance for neuromodulator placement. Thirty-seven healthy volunteers (29 Caucasians, six African Americans, two Asians) with a mean age of 39.84±14.4years [range: 22-73] were enrolled. 3D images of the forehead were analyzed using a Vectra H1 camera system computing skin displacement vectors between the noncontracted and the maximally contracted forehead of the volunteers. Relationships between the shape of the horizontal forehead lines (straight vs wavy) and the forehead motion pattern were calculated. Independent of age or gender, a greater forehead motion angle was associated with the presence of wavy forehead lines 21.34°±5.9 with P<0.001, whereas straight forehead lines were associated with a smaller forehead motion angle 6.68°±2.9 P<0.001. Females had more frequently straight horizontal forehead lines versus males: 68.4% vs 44.4% (P=0.037). Young volunteers (<39.8years) did not differ in their mean forehead motion angle when compared to older volunteers (>39.8years): 13.70°±9.0 vs 12.39°±8.0 with P=0.530. Injections of neuromodulators in the forehead can be individualized by respecting the shape of the horizontal forehead lines. Wavy lines require injection points that are located more laterally, whereas straight lines require more centrally located injection points.

Low velocity impact on crash components with steel skins and polymer foam cores

Energy absorbing systems are extensively used in the automotive industry to ensure crashworthiness. Such crash components could typically consist of a sandwich structure with thin ductile plates as skins and a cellular foam as core to dissipate the kinetic energy. In a previous study, the quasi-static behaviour of two polymeric foam types with different densities, namely extruded polystyrene (XPS) and expanded polypropylene (EPP), used as core material in typical crash components was examined. The investigation involved a large number of compression tests of the core materials loaded in different material directions and indentation tests on sandwich structures in different configurations. In the present study, low-velocity impact tests are conducted in a drop tower on the same target configurations consisting of 0.8 mm thick skins of Docol 600DL steel and the various foams as core. During testing, the dropped mass was kept constant at approximately 15 kg, while the impact velocity varied between 5 and 10 m/s. The impact force was registered by the instrumented striker of the drop tower, and these measurements were used to obtain the displacement of the striker and the energy absorption of the different crash components. In addition, high-speed cameras and 3D-DIC were used to measure the out-of-plane displacement of the back skin. The presented results indicate that to minimise the weight and at the same time maximize the energy absorption of the crash component, a low density foam should be used as core material. It is also shown that by proper design, it is possible to optimize the protection level of such components, at least within a given velocity range.

Motion Quantification and Automated Correction in Clinical RSOM.

Raster-scan optoacoustic mesoscopy (RSOM) offers high-resolution non-invasive insights into skin pathophysiology, which holds promise for disease diagnosis and monitoring in dermatology and other fields. However, RSOM is quite vulnerable to vertical motion of the skin, which can depend on the part of the body being imaged. Motion correction algorithms have already been proposed, but they are not fully automated, they depend on anatomical segmentation pre-processing steps that might not be performed successfully, and they are not site- specific. Here, we determined for the first time the magnitude of the micrometric vertical skin displacements at different sites on the body that affect RSOM. The quantifi- cation of motion allowed us to develop a site-specific correction algorithm. The algorithm is fully automated and does not need prior anatomical information. We found that the magnitude of the vertical motion depends strongly on the site of imaging and is caused by breathing, heart beating, and arterial pulsation. The developed algorithm resulted in more than 2-fold improvement in the signal-to-noise ratio of the reconstructed images at every site tested. Proposing an effective automated motion correction algorithm paves the way for realizing the full clinical potential of RSOM.

Person-Specific Heart Rate Estimation With Ultra-Wideband Radar Using Convolutional Neural Networks

Vital-sign estimation using ultra-wideband (UWB) radar is preferable because it is contactless and less privacy-invasive. Recently, many approaches have been proposed for estimating heart rate from UWB radar data. However, their performance is still not reliable enough for practical applications. To improve the accuracy, this study employs convolutional neural networks to learn the special patterns of the heartbeats. In the proposed system, skin displacements of the target person are measured using UWB radar, and the radar signal is converted to a two-dimensional matrix, which is used as the input of the designed neural networks. Meanwhile, two triangular waves corresponding to the peaks and valleys in an electrocardiogram are adopted as the output of the networks. The proposed system then identifies each individual and estimates the heart rate automatically based on the already trained neural networks. The estimation error of the interbeat interval computed using our approach was reduced to 4.5 ms in the best case; and 48.5 ms in the worst case. Experiment results show that the proposed approach significantly outperforms a conventional method. The proposed machine learning approach achieves both personal identification and heart rate estimation simultaneously using UWB radar data for the first time. Moreover, this study found that using the respiration and heartbeat components together may enhance the accuracy of heart rate estimation, which is counter-intuitive, because the respiration is usually believed to interfere with the heartbeat.

Non-contact Quantification of Jugular Venous Pulse Waveforms from Skin Displacements

The jugular venous (JV) pressure waveform is a non-invasive, proven indicator of cardiovascular disease. Conventional clinical methods for assessing these waveforms are often overlooked because they require specialised expertise, and are invasive and expensive to implement. Recently, image-based methods have been used to quantify JV pulsation waveforms on the skin as an indirect way of estimating the pressure waveforms. However, these existing image-based methods cannot explicitly measure skin deformations and rely on the use of photoplethysmography (PPG) devices for identification of the pulsatile waveforms. As a result, they often have limited accuracy and robustness and are unsuitable in the clinical environment. Here, we propose a technique to directly measure skin deformations caused by the JV pulse using a very accurate subpixel registration algorithm. The method simply requires images obtained from the subject’s neck using a commodity camera. The results show that our measured waveforms contained all of the essential features of diagnostic JV waveforms in all of 19 healthy subjects tested in this study, indicating a significantly important capability for a potential future diagnostic device. The shape of our measured JV displacement waveforms was validated using waveforms measured with a laser displacement sensor, where the average correlation score between the two waveforms was 0.93 ± 0.05. In addition, synchronously recorded ECG signals were used to verify the timings of diagnostic features of the measured waveforms. To our knowledge, this is the first use of image registration for direct measurement of JV displacement waveforms. Significant advantages of our novel method include the high precision of our measurements, and the ability to use ordinary cameras, such as those in modern mobile phones. These advantages will enable the development of affordable and accessible devices to measure JV waveforms for cardiac diagnostics in the clinical environment. Future devices based on this technology may provide viable options for telemedicine applications, point of care diagnostics, and mobile-based cardiac health monitoring systems.

Implementation of a thermomechanical model to simulate laser heating in shrinkage tissue (effects of wavelength, laser irradiation intensity, and irradiation beam area)

Advancements in the use of laser technology in the medical field have motivated the widespread use of thermal energy to treat a wide variety of diseases and injuries. During laser-induced thermotherapy, the tissue gains heat from laser irradiation and its shape is deformed due to non-uniform temperature distribution. To describe the phenomenon adequately, the mathematical model that considers both heat transfer and mechanical deformation is needed. In this study, the formulation of mathematical model describing coupled heat transfer and mechanical deformation of tissue subjected to laser-induced thermotherapy is numerically implemented. The effects of laser irradiation time, wavelength, laser intensity, laser beam radius and blood perfusion rate on temperature distribution, Von Mises stress distribution, and displacement of the layered skin during laser irradiation are systematically investigated. The values obtained provide an indication of limitations that must be considered in administering laser-induced thermotherapy.

The posterior temporal supraSMAS minimally invasive lifting technique using soft-tissue fillers.

To investigate the effectiveness of the posterior temporal supraSMAS minimally invasive lifting technique and compared it to experiments performed in fresh human body donors by applying skin vector displacement measurement technology. A total of 15 patients (14 females/1 male) with a mean age of 37.1±9.4years and a mean body mass index of 21.4±3.3kg/m2 were included into this observational analysis. The injection procedure was additionally performed in 2 male and 1 female fresh body donors with a mean age of 85.67±9.7years and a mean body mass index of 23.83±4.7kg/m2 . Different grades of skin laxity, variable amounts of product, and the application with and without subcision were tested and measured via three-dimensional reconstructions and surface displacement vectors using Vectra software with VAM module. Esthetic outcome was rated by an independent professional observer and by the patient immediately after the treatment (76.67%±17.6% vs 66.67%±18.1%) (P=0.001) and after 1month (80.00%±14.0% vs 75.00%±21.1%) (P=0.19). Skin laxity, subcision, and the application of more than 1.0cc per side resulted in our experimental setting in a smaller magnitude of skin displacement vectors indicating a reduced lifting effect. The posterior temporal supraSMAS minimally invasive lifting procedure seems to be a valid technique to treat temporal volume loss and to reduce the signs of age-related changes in the middle and lower face, ie "marionett line" and jowl deformity.

Understanding Displacements of the Gel Liner for Below Knee Prosthetic Users.

Many people with amputation utilize a prosthetic device to maintain function and ambulation. During the use of the prosthetic device, their residual limbs can develop wounds called pressure ulcers. The formation of these wounds has been linked to deformation and loading conditions of the skin and deeper tissues. Our research objective was to develop a complete profile of displacements on the gel liner at the interface with the socket during walking in transtibial amputees. Displacements for seven regions along the limb were quantified in addition to six calculations of displacement and three rotations relative to the prosthetic socket. The largest displacements were observed in the distal region of the gel liner, near the pin locking mechanism on the gel liner. Displacements were uneven throughout the liner with distal regions showing higher displacements. This mechanics-based information, combined with clinical information, will allow us to understand the local skin and muscle displacements, and will provide insights regarding localized tissue breakdown. Knowledge of how the liner displaces within the prosthetic socket can also help prosthetists modify designs to reduce these displacements, and reduce the potential for shear on the skin and in deeper tissues.

Precise Detection of Wrist Pulse Using Digital Speckle Pattern Interferometry.

Pulse diagnosis is one of the four diagnostic methods of traditional Chinese medicine. However it suffers from the lack of objective and efficient detection method. We propose a noncontact optical method to detect human wrist pulse, aiming at the precise determination of the temporal and spatial distributions of pulse. The method uses the spatial-carrier digital speckle pattern interferometry (DSPI) to measure the micro/nanoscale skin displacement dynamically. Significant improvements in DSPI measurement have been made to allow the DSPI to detect the comprehensive information of the arterial pulsation at locations of Cun, Guan, and Chi. The experimental results prove that the spatiotemporal distributions of pulse can be obtained by the proposed method. The obtained data can be further used to describe most of the pulse parameters such as rate, rhythm, depth, length, width, and contour.

Non-contact and through-clothing measurement of the heart rate using ultrasound vibrocardiography

We present a novel non-contact system for monitoring the heart rate on human subjects with clothes. Our approach is based on vibrocardiography, and measures locally skin displacements. Vibrocardiography with a laser Doppler vibrometer already allows monitoring of this vital sign, but can only be used on bare skin and requires an expensive piece of equipment. We propose here to use an airborne pulse-Doppler ultrasound system operating in the 20–60 kHz range, and comprised of an emitter focusing the ultrasound pulses on skin and a microphone recording the reflected waves. Our implementation was validated in vitro and on two healthy human subjects, using simultaneously laser vibrocardiography and electrocardiography as references. Accurate measurements of the heart rate on clothed skin suggest that our non-contact ultrasonic method could be implemented both inside and outside the clinical environment, and therefore benefit both medical and safety applications.

The effect of rigid taping with tension on mechanical displacement of the skin and change in pain perception

ObjectivesTo investigate the effect of rigid taping that induces mechanical displacement of the skin on pain perception. DesignSingle group experiment design with repeated measures. MethodsTwenty-three active healthy volunteers (12 men and 11 women) participated in the study. All participants received three different taping procedures: no tape, taping with tension, and taping without tension. The order of three taping conditions was randomised. Skin displacement was measured during taping with tension. A pressure algometer was used to measure the level of pain perception once before taping, and again after each taping condition, in one testing session. The participants were blind to the values of their pressure pain threshold (PPT) during the experimental period. ResultsThe mean±SD skin displacement in the condition of taping with tension was 2.58±0.49cm. There were significant differences in PPT between taping with tension and taping without tension (mean difference (mean diff)±standard error (SE) 36.43±4.22kPa, p=0.000) and no tape (mean diff±SE 44.31±3.13kPa, p=0.000). No significant difference in PPT between no tape and taping without tension was found (mean diff±SE 7.88±2.83kPa, p=0.067). ConclusionsTaping with tension increases the threshold of pressure pain perception. Therefore, stretch and compression caused by rigid taping with tension could disturb the nociceptive signal transmission and alter pain perception.

Noninvasive iPhone Measurement of Left Ventricular Ejection Fraction Using Intrinsic Frequency Methodology.

The study is based on previously reported mathematical analysis of arterial waveform that extracts hidden oscillations in the waveform that we called intrinsic frequencies. The goal of this clinical study was to compare the accuracy of left ventricular ejection fraction derived from intrinsic frequencies noninvasively versus left ventricular ejection fraction obtained with cardiac MRI, the most accurate method for left ventricular ejection fraction measurement. After informed consent, in one visit, subjects underwent cardiac MRI examination and noninvasive capture of a carotid waveform using an iPhone camera (The waveform is captured using a custom app that constructs the waveform from skin displacement images during the cardiac cycle.). The waveform was analyzed using intrinsic frequency algorithm. Outpatient MRI facility. Adults able to undergo MRI were referred by local physicians or self-referred in response to local advertisement and included patients with heart failure with reduced ejection fraction diagnosed by a cardiologist. Standard cardiac MRI sequences were used, with periodic breath holding for image stabilization. To minimize motion artifact, the iPhone camera was held in a cradle over the carotid artery during iPhone measurements. Regardless of neck morphology, carotid waveforms were captured in all subjects, within seconds to minutes. Seventy-two patients were studied, ranging in age from 20 to 92 years old. The main endpoint of analysis was left ventricular ejection fraction; overall, the correlation between ejection fraction-iPhone and ejection fraction-MRI was 0.74 (r = 0.74; p < 0.0001; ejection fraction-MRI = 0.93 × [ejection fraction-iPhone] + 1.9). Analysis of carotid waveforms using intrinsic frequency methods can be used to document left ventricular ejection fraction with accuracy comparable with that of MRI. The measurements require no training to perform or interpret, no calibration, and can be repeated at the bedside to generate almost continuous analysis of left ventricular ejection fraction without arterial cannulation.

テクスチャ面に対する指表面挙動の観察に関する諸考察

テクスチャ面に対する指表面挙動の観察に関する諸考察